U.S. patent application number 14/704147 was filed with the patent office on 2015-11-12 for light emitting device, surface light source device and display apparatus.
The applicant listed for this patent is Enplas Corporation. Invention is credited to Yu KAMIJO, Hiroshi TAKATORI.
Application Number | 20150323729 14/704147 |
Document ID | / |
Family ID | 54367705 |
Filed Date | 2015-11-12 |
United States Patent
Application |
20150323729 |
Kind Code |
A1 |
TAKATORI; Hiroshi ; et
al. |
November 12, 2015 |
LIGHT EMITTING DEVICE, SURFACE LIGHT SOURCE DEVICE AND DISPLAY
APPARATUS
Abstract
A light emitting device includes a substrate in which a specular
reflection area that specularly reflects reaching light is disposed
on one surface, a light emitting element disposed on the substrate
to emit light at least from a side surface, and a light flux
controlling member disposed over the light emitting element to
control a distribution of light to be emitted from the light
emitting element. The light flux controlling member includes a rear
surface disposed closer to the substrate, an incidence surface
being an inner surface of a recess opening toward the rear surface
and receiving light emitted from the light emitting element, and an
emission surface emitting at least a part of the light incident
through the incidence surface toward an outside. An outer edge
portion of the specular reflection area is positioned outside an
opening edge portion of the recess.
Inventors: |
TAKATORI; Hiroshi; (Saitama,
JP) ; KAMIJO; Yu; (Saitama, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Enplas Corporation |
Saitama |
|
JP |
|
|
Family ID: |
54367705 |
Appl. No.: |
14/704147 |
Filed: |
May 5, 2015 |
Current U.S.
Class: |
362/606 ;
362/612 |
Current CPC
Class: |
G02F 1/133603 20130101;
G02B 6/0073 20130101; G02F 2001/133607 20130101; G02B 6/0051
20130101; G02B 6/0055 20130101; G02F 1/133605 20130101 |
International
Class: |
F21V 8/00 20060101
F21V008/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 8, 2014 |
JP |
2014-097174 |
Claims
1. A light emitting device comprising: a substrate in which a
specular reflection area that specularly reflects reaching light is
disposed on one surface; a light emitting element disposed on the
substrate to emit light at least from a side surface; and a light
flux controlling member disposed over the light emitting element to
control a distribution of light to be emitted from the light
emitting element, wherein: the light flux controlling member
includes: a rear surface disposed closer to the substrate, an
incidence surface being an inner surface of a recess opening toward
the rear surface and receiving light emitted from the light
emitting element, and an emission surface emitting at least a part
of the light incident through the incidence surface toward an
outside; and an outer edge portion of the specular reflection area
is positioned outside an opening edge portion of the recess.
2. The light emitting device according to claim 1, wherein: the
emission surface is disposed opposite to the rear surface; and the
outer edge portion of the specular reflection area is disposed
inside a position where a peak amount of light is indicated which
is Fresnel-reflected at the emission surface and reaches the rear
surface, out of light emitted from the light emitting element and
being incident through the incidence surface.
3. A surface light source device comprising: the light emitting
device according to claim 1; and a light diffusing member that
transmits light from the light emitting device while diffusing the
light.
4. A display apparatus comprising: the surface light source device
according to claim 3; and a display member to be irradiated with
light emitted from the surface light source device.
5. A surface light source device comprising: the light emitting
device according to claim 2; and a light diffusing member that
transmits light from the light emitting device while diffusing the
light.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is entitled to and claims the benefit of
Japanese Patent Application No. 2014-097174, filed on May 8, 2014,
the disclosure of which including the specification, drawings and
abstract is incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to a light emitting device
having a light emitting element and a light flux controlling
member, a surface light source device and an illumination apparatus
having the light emitting device.
BACKGROUND ART
[0003] Some transmission type image display apparatuses such as
liquid crystal display apparatuses use a direct surface light
source device. In recent years, surface light source devices having
a plurality of light emitting elements as the light source have
been used.
[0004] For example, the surface light source device includes a
substrate, a plurality of light emitting elements, a plurality of
light flux controlling members, and a light diffusion plate. The
plurality of light emitting elements is disposed on the substrate
in a matrix manner. The light flux controlling member that expands
light emitted from each of the light emitting elements in the plane
direction of the substrate is disposed over each of the light
emitting elements. The light emitted from each of the light
emitting elements is diffused by the light flux controlling member
to irradiate a member to be irradiated (e.g., liquid crystal panel)
in a planar manner (see, e.g., PTL 1).
[0005] FIG. 1 is a drawing illustrating the configuration of a
surface light source device (back light device) disclosed in PTL 1.
As illustrated in FIG. 1, back light device (surface light source
device) 10 disclosed in PTL 1 includes a mounting substrate 20 in
which insulating layer 21, wiring layer 22 and resist layer 23 are
laminated in order, package 30 disposed on mounting substrate 20
and including a light emitting chip (light emitting element) 32
that emits light through its upper surface, the package 30 being
electrically connected to mounting substrate 20 via solder layer
31, diffusion lens (light flux controlling member) 40 disposed on
mounting substrate 20 in such a manner as to cover package 30 to
control the distribution of light emitted from light emitting chip
32, and diffusion plate 50 that transmits light emitted from
diffusion lens 40 while diffusing the light. Diffusion lens 40 has
lens part 41 that expands light emitted from package 30, and a
fixing part 42 for fixing lens part 41 to mounting substrate 20 via
adhesive 46. Lens part 41 has bottom surface 43 closer to mounting
substrate 20, recessed light incidence surface 44 opening toward
bottom surface 43, and light emission surface 45 disposed opposite
to light incidence surface 44.
[0006] The light emitted from light emitting chip 32 enters
diffusion lens 40 through light incidence surface 44. The light
having entered diffusion lens 40 is emitted toward the outside of
diffusion lens 40 through light emission surface 45. Then, the
light emitted toward the outside is transmitted through diffusion
plate 50 while being diffused to thereby irradiate a member to be
irradiated in a planar manner.
[0007] In addition, PTL 2 discloses a flip-chip type LED that emits
light from the side surface. The LED disclosed in PTL 2 is designed
to emit light from the side surface by disposing a reflective film
on the upper surface of a phosphor layer that emanates light.
CITATION LIST
Patent Literature
PTL 1
Japanese Patent Application Laid-Open No. 2013-218940
PTL 2
Japanese Unexamined Patent Application Publication (Translation of
PCT Application) No. 2010-537400
SUMMARY OF INVENTION
Technical Problem
[0008] Back light device 10 disclosed in PTL 1 optimizes the
efficiency of the incidence of light emitted from light emitting
chip 32 into diffusion lens 40 by disposing diffusion lens 40
upward over the upper surface of package 30. On the other hand,
there is a possibility for many reasons that the LED that emits
light from the side surface as disclosed in PTL 2 may be installed
in back light device 10 disclosed in PTL 1.
[0009] However, when the LED disclosed in PTL 2 is installed in
back light device 10 disclosed in PTL 1, the LED disclosed in PTL 2
emits light from the side surface, and thus a part of the light
emitted from the side surface of the LED reaches mounting substrate
20. Then, a part of the light having reached mounting substrate 20
is diffused at resist layer 23 to enter diffusion lens 40 through
bottom surface 43 of diffusion lens 40, so that the light having
entered diffusion lens 40 has a risk of being uncontrollable light.
Thus, the surface light source device (back light device) disclosed
in PTL 1 has a problem of not being able to control light emitted
from the light emitting element to be a desired light distribution
when used for the light emitting element that emits light from the
side surface.
[0010] Therefore, an object of the present invention is to provide
a light emitting device having a light emitting element that emits
light at least from the side surface and being capable of
controlling light emitted from the light emitting element to be a
desired light distribution.
[0011] Another object of the present invention is to provide a
surface light source device and a display apparatus having the
light emitting device.
Solution to Problem
[0012] A light emitting device of the present invention is a light
emitting device including: a substrate in which a specular
reflection area that specularly reflects reaching light is disposed
on one surface; a light emitting element disposed on the substrate
to emit light at least from a side surface; and a light flux
controlling member disposed over the light emitting element to
control a distribution of light to be emitted from the light
emitting element, wherein: the light flux controlling member
includes a rear surface disposed closer to the substrate, an
incidence surface being an inner surface of a recess opening toward
the rear surface and receiving light emitted from the light
emitting element, and an emission surface emitting at least a part
of the light incident through the incidence surface toward an
outside; and an outer edge portion of the specular reflection area
is positioned outside an opening edge portion of the recess.
[0013] A surface light source device of the present invention
includes the light emitting device of the present invention, and a
light diffusing member that transmits light from the light emitting
device while diffusing the light.
[0014] A display apparatus of the present invention includes the
surface light source device of the present invention, and a display
member to be irradiated with light emitted from the surface light
source device.
Advantageous Effects of Invention
[0015] According to the present invention, it is possible to
properly control the distribution of light emitted from a light
emitting element, while having a light emitting element that emits
light from the side surface. Accordingly, the surface light source
device and the display apparatus according to the present invention
have less luminance unevenness.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 is a drawing illustrating a configuration of a back
light device disclosed in PTL 1;
[0017] FIGS. 2A and 2B are drawings illustrating a configuration of
a surface light source device according to Embodiment 1;
[0018] FIGS. 3A and 3B are sectional views of the surface light
source device according to Embodiment 1;
[0019] FIG. 4 is a partially enlarged sectional view of the surface
light source device according to Embodiment 1;
[0020] FIGS. 5A and 5B are partially enlarged sectional views of a
light emitting device according to Embodiment 1, and of a substrate
and a light emitting element, respectively;
[0021] FIGS. 6A and 6B are views of optical path near a light
emitting element in a light emitting device for comparison, and of
optical path near a light emitting element in the light emitting
device according to Embodiment 1, respectively;
[0022] FIG. 7 is a view of optical path of the light emitting
device according to Embodiment 1; and
[0023] FIGS. 8A and 8B are partially enlarged sectional views of a
surface light source device according to Embodiment 2, and of a
light emitting device according to Embodiment 2, respectively.
DESCRIPTION OF EMBODIMENTS
[0024] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying drawings. In
the following description, as a typical example of the surface
light source device according to the present invention, a surface
light source device suitable as a back light of a liquid crystal
display apparatus will be described. When used with a member to be
irradiated (e.g., liquid crystal panel) with light from the surface
light source device, the surface light source device can be used as
a display apparatus.
Embodiment 1
Configurations of Surface Light Source Device
[0025] FIGS. 2A, 2B, 3A and 3B are drawings illustrating the
configuration of surface light source device 100 according to
Embodiment 1 of the present invention. FIG. 2A is a plan view of
surface light source device 100 according to the present
embodiment, and FIG. 2B is a front view of surface light source
device 100. FIG. 3A is a sectional view taken along line A-A
illustrated in FIG. 2B, and FIG. 3B is a sectional view taken along
line B-B illustrated in FIG. 2A.
[0026] As illustrated in FIGS. 2A, 2B, 3A and 3B, surface light
source device 100 according to the present embodiment includes
casing 120, light diffusing member 140, and a plurality of light
emitting devices 160. A plurality of light emitting devices 160 is
disposed over bottom plate 122 of casing 120 in a matrix manner.
The inner surface of bottom plate 122 functions as a diffusion and
reflection surface. In addition, the top plate of casing 120 is
provided with an opening. The size of the opening is, for example,
about 400 mm.times.about 700 mm (32 inches), although the size
thereof is not particularly limited.
[0027] Light diffusing member 140 is disposed in such a manner as
to cover the opening of casing 120. Light diffusing member 140 is a
plate-like member having a light diffusing property, and transmits
light emitted from light emitting device 160 while diffusing the
light. Typically, the size of light diffusing member 140 is
substantially the same as that of a member to be irradiated, such
as a liquid crystal panel. For example, light diffusing member 140
is formed of optically transparent resins such as
polymethylmethacrylate (PMMA), polycarbonate (PC), polystyrene
(PS), and styrene methyl methacrylate copolymerization resin (MS).
In order to provide a light diffusing property, fine irregularities
are formed on the surface of light diffusing member 140, or light
diffusers such as beads are dispersed inside light diffusing member
140.
[0028] (Configuration of Light Emitting Device)
[0029] FIG. 4 is a partially enlarged sectional view of surface
light source device 100 (a partially enlarged sectional view of
FIG. 3B). FIG. 5A is a partially enlarged sectional view of light
emitting device 160 (a partially enlarged sectional view of FIG.
4), and FIG. 5B is a partially enlarged plan view of substrate 170
and light emitting element 180.
[0030] As illustrated in FIGS. 4, 5A and 5B, each of a plurality of
light emitting devices 160 has substrate 170, light emitting
element 180, and light flux controlling member 190.
[0031] Substrate 170 is a tabular member, and supports light
emitting element 180 and light flux controlling member 190.
Substrate 170 has substrate main body 171, two copper foil layers
172, resist layer 173, and two plated layers 174.
[0032] Substrate main body 171 is a tabular insulator. The shape of
substrate main body 171 in a plan view is not particularly limited.
The shape of substrate main body 171 in a plan view either may be
circular, or may be polygonal. In the present embodiment, the shape
of substrate main body 171 in a plan view is rectangular. In
addition, the thickness of substrate main body 171 is not
particularly limited, and may be appropriately set. Further, the
material for composing substrate main body 171 is not particularly
limited insofar as the material is an insulator. In the present
embodiment, substrate main body 171 is a glass epoxy substrate.
[0033] Two copper foil layers 172 are spaced apart from each other
on substrate main body 171. Two copper foil layers 172 interpose
resist layer 173 therebetween, and are insulated from each other.
Two copper foil layers 172 are connected respectively to two
terminals of light emitting element 180 through plated layer 174
and solder layer 176 to function as wiring. The arrangement of two
copper foil layers 172 on substrate main body 171 is not
particularly limited insofar as two copper foil layers 172 function
as wiring of light emitting element 180, and may be appropriately
set. In addition, the thickness of copper foil layer 172 is not
particularly limited, and may be appropriately set.
[0034] Resist layers 173 are disposed on and between two copper
foil layers 172, and mainly protect two copper foil layers 172. A
material composing resist layer 173 is not particularly limited
insofar as the material has an insulation property and can protect
copper foil layers 172, and may be appropriately selected from
known materials.
[0035] Plated layers 174 are disposed respectively on two copper
foil layers 172. Plated layer 174 electrically connects solder
layer 176 to which light emitting element 180 is fixed to copper
foil layer 172. The type of plated layer 174 is not particularly
limited insofar as it has electrical conductivity. Examples of
plated layer 174 include solder plating. In addition, the surface,
closer to light emitting element 180, of plated layer 174 functions
as specular reflection area 175 that specularly reflects light
emitted from light emitting element 180. That is, specular
reflection area 175 is disposed on one surface of substrate 170 in
such a manner as to surround the periphery of light emitting
element 180 except a part of the periphery. In the present
embodiment, the surface of plated layer 174 is subjected to mirror
finishing, and thus the surface of plated layer 174 functions as
specular reflection area 175. The shape of specular reflection area
175 in a plan view is not particularly limited. In the present
embodiment, the shape of specular reflection area 175 in a plan
view is substantially semicircular. It is noted that surface light
source device 100 according to the present embodiment has one
feature of having specular reflection area 175 in a specific area
directly under light flux controlling member 190. Thus, the
position of specular reflection area 175 will be described
later.
[0036] Light emitting element 180 is a light source of surface
light source device 100, and is disposed over specular reflection
area 175 of substrate 170. Light emitting element 180 is not
particularly limited insofar as light emitting element 180 is a
light source that emits light at least from the side surface. In
the present embodiment, light emitting element 180 is a flip type
light emitting diode (LED) that emits light from the top surface
and the side surface. Two terminals at the bottom surface of light
emitting element 180 are fixed respectively to plated layers 174 to
allow light emitting element 180 to be electrically connected to
copper foil layers 172.
[0037] Light flux controlling member 190 is a diffusion lens that
controls the distribution of light emitted from light emitting
element 180, and is fixed over substrate 170. Light flux
controlling member 190 is disposed over light emitting element 180
such that its central axis CA coincides with optical axis LA of
light emitting element 180. A gap is formed between the surface of
substrate 170 on which light emitting element 180 is mounted and
rear surface 191 of light flux controlling member 190, for
releasing heat generated from light emitting element 180 to the
outside. The distance in the direction of central axis CA between
the rear surface and substrate 170 is preferably shorter, although
the distance is not particularly limited. It is noted that the term
"optical axis LA of light emitting element" means the central light
beam of a three-dimensional light flux from light emitting element
180.
[0038] Light flux controlling member 190 is formed by integral
molding. The material for light flux controlling member 190 is not
particularly limited insofar as the light of a desired wavelength
can pass through the material. Examples of the material for light
flux controlling member 190 include optically transparent resins
such as polymethylmethacrylate (PMMA), polycarbonate (PC) and epoxy
resin (EP), and glass.
[0039] In light emitting device 160 according to the present
embodiment, light emitted from each light emitting element 180 is
expanded by each light flux controlling member 190 in such a manner
as to irradiate a wider range of light diffusing member 140. Light
emitted from each light emitting device 160 is diffused further by
light diffusing member 140. Consequently, surface light source
device 100 according to the present embodiment can evenly irradiate
a planar member to be irradiated (e.g., liquid crystal panel).
[0040] (Configuration of Light Flux Controlling Member)
[0041] As illustrated in FIG. 4, light flux controlling member 190
includes rear surface 191, incidence surface 192, and emission
surface 193. In addition, in light flux controlling member 190,
flange 195 may be disposed between rear surface 191 and emission
surface 193. Further, rear surface 191 may have a leg thereon for
forming a gap between light emitting device 180 and light flux
controlling member 190.
[0042] Rear surface 191 is a planar surface disposed closer to
substrate 170 and extending in the direction orthogonal to central
axis CA (optical axis LA of light emitting element 180). The
central portion of rear surface 191 has opening recess 194 of which
inner surface is incidence surface 192. The shape of rear surface
191 in a plan view is not particularly limited. In the present
embodiment, the shape of rear surface 191 in a plan view is
circular.
[0043] Incidence surface 192 receives light emitted from a light
source. Incidence surface 192 is an inner surface of recess 194
opening toward rear surface 191. Incidence surface 192 is a
rotationally symmetrical plane, and the central axis of incidence
surface 192 coincides with central axis CA of light flux
controlling member 190.
[0044] Emission surface 193 is disposed opposite to rear surface
191. Emission surface 193 emits at least a part of light having
entered incidence surface 192. Emission surface 193 has first
emission surface 193a positioned on the periphery of central axis
CA, second emission surface 193b formed continuously around first
emission surface 193a, and third emission surface 193c connecting
second emission surface 193b to flange 195. First emission surface
193a is a smooth curved surface being convex downward (toward light
emitting element 180). Second emission surface 193b is a smooth
curved surface being convex upward (toward light diffusing member
140) positioned around first emission surface 193a. Third emission
surface 193c is a smooth curved surface positioned around second
emission surface 193b. In the cross-section illustrated in FIG. 4,
the cross-section of third emission surface 193c either may be
linear, or may be curved.
[0045] Flange 195 is positioned between the outer peripheral
portion of emission surface 193 and the outer peripheral portion of
rear surface 191, and protrudes in the direction orthogonal to
central axis CA (optical axis LA of light emitting element 180).
While flange 195 is not always necessary, providing flange 195
makes it easier to handle and align light flux controlling member
190. The thickness of flange 195 is not particularly limited, and
is determined taking account of an area required for emission
surface 193, the molding property of flange 195, or the like. When
light flux controlling member 190 is manufactured by injection
molding, gate mark (illustration omitted) sometimes may be formed
on flange 195. In addition, a plurality of protruding portions
(illustration omitted) for allowing an apparatus for manufacturing
surface light source device 100 to recognize the direction of light
flux controlling member 190 may be formed on flange 195.
[0046] In addition, light flux controlling member 190 may have a
plurality of legs. The legs are columnar members protruding
downward (toward light emitting element 180) from rear surface 191
around recess 194. A plurality of legs performs a function of
aligning light flux controlling member 190 at an appropriate
position with respect to light emitting element 180.
[0047] In light flux controlling member 190 according to the
present embodiment, light emitted from light emitting element 180
enters light flux controlling member 190 through incidence surface
192. Then, a part of the incident light is emitted toward the
outside of light flux controlling member 190 through emission
surface 193. In addition, a part of the incident light is reflected
toward rear surface 191 by Fresnel reflection. In light emitting
device 160 according to the present embodiment, specular reflection
area 175 is designed also taking account of the Fresnel-reflected
light.
[0048] Next, the positional relationship between light flux
controlling member 190 and specular reflection area 175 will be
described with reference to FIGS. 6A and 6B. FIGS. 6A and 6B are
views of optical path near a light emitting element in a light
emitting device for comparison, and of optical path near the light
emitting element in the light emitting device according to the
present embodiment, respectively. The light emitting device
illustrated in FIG. 6A and the light emitting device illustrated in
FIG. 6B differ from each other in the size of specular reflection
area 175, and consequently the positions of the outer edges of
specular reflection areas 175 differ from each other.
[0049] As illustrated in FIG. 6A, when the outer edge portion of
specular reflection area 175 is positioned inside the opening edge
portion of recess 194 (positioned closer to central axis CA), a
part of light emitted from the side surface of light emitting
element 180 undesirably reaches resist layer 173 directly. The
light thus having reached resist layer 173 is scattered by resist
layer 173 to undesirably become uncontrollable light.
[0050] On the other hand, as illustrated in FIG. 6B, also when the
outer edge portion of specular reflection area 175 is positioned
outside the opening edge of recess 194, a part of light emitted
from the side surface of light emitting element 180 reaches
substrate 170. However, all the light having reached substrate 170
is specularly reflected at specular reflection area 175 to enter
light flux controlling member 190 through incidence surface 192.
Thus, the light specularly reflected at specular reflection area
175 may be properly controlled by emission surface 193 in the same
manner as light having entered light flux controlling member 190
directly from light emitting element 180. That is, when the outer
edge portion of specular reflection area 175 is positioned outside
the opening edge of recess 194, the distribution of light emitted
from light emitting element 180 can be properly controlled, even in
the case of using light emitting element 180 that emits light from
the side surface.
[0051] FIG. 7 is a view of optical path of light emitted from the
top surface of light emitting element 180. As illustrated in FIG.
7, light emitted from the top surface of light emitting element 180
enters light flux controlling member 190 through incidence surface
192. The light having entered light flux controlling member 190
reaches emission surface 193 to be emitted toward the outside
through emission surface 193 (solid line arrow). At that time,
light is refracted due to the shape of emission surface 193, and
thus the traveling direction of light is controlled. On the other
hand, a part of the light having reached emission surface 193 is
reflected at emission surface 193 (Fresnel reflection) to reach
rear surface 191 (broken line arrow) that faces substrate 170 where
light emitting element 180 is mounted. The light having reached
rear surface 191 then reaches substrate 170. Thus, when the light
having been Fresnel-reflected at emission surface 193 reaches
substrate 170, diffuse reflection at resist layer 173 can inhibit a
bright part from generating on light diffusing member 140 above
light emitting device 160, compared with the reflection at specular
reflection area 175 toward emission surface 193. Accordingly, the
outer edge portion of specular reflection area 175 is preferably
inside a position (closer to central axis CA) where much of the
light having been Fresnel-reflected at emission surface 193 reaches
rear surface 191 (resist layer 173) (inside a position where the
amount of light having reached indicates the peak). The position on
rear surface 191 where much of the light having been
Fresnel-reflected at emission surface 193 of light flux controlling
member 190 reaches can be determined by simulation or experiment,
as disclosed in Japanese Patent Application Laid-Open No.
2012-004078. It is noted that even when the outer edge portion of
specular reflection area 175 is outside the position where the
light having been Fresnel-reflected reaches resist layer 173, light
from the side surface of light emitting element 180 hardly reaches
that position, and thus the effect is saturated.
[0052] (Effect)
[0053] As described above, since specular reflection area 175
larger than the opening of recess 194 is disposed around light
emitting element 180, light emitting device 160 according to
Embodiment 1 can properly control light emitted from light emitting
element 180 even when light emitting device 180 that emits light
from the side surface is used. Therefore, surface light source
device 100 according to the present invention has less luminance
unevenness.
Embodiment 2
[0054] Surface light source device 200 of Embodiment 2 differs from
surface light source device 100 of Embodiment 1 only in the shape
of the light flux controlling member in the light emitting device.
Therefore, only light emitting device 260 according to Embodiment 2
will be described.
[0055] (Configurations of Light Emitting Device and Light Flux
Controlling Member)
[0056] FIGS. 8A and 8B are partially enlarged sectional views of
surface light source device 200 according to Embodiment 2, and of
light emitting device 260 according to Embodiment 2, respectively.
As illustrated in these drawings, light emitting device 260
according to Embodiment 2 has substrate 170, light emitting element
180, and light flux controlling member 290. It is noted that
substrate 170 and light emitting element 180 are the same as those
of Embodiment 1, and thus the descriptions therefor will be
omitted.
[0057] Light flux controlling member 290 according to Embodiment 2
includes rear surface 191, incidence surface 292, reflection
surface 296, and emission surface 293. Light flux controlling
member 290 according to Embodiment 2 allows light having been
emitted from the top surface of light emitting element 180 and
having entered top surface 297 of incidence surface 292 to be
reflected sideward at reflection surface 296, and then allows the
light to be emitted sideward through emission surface 293 toward
the outside of light flux controlling member 290. In addition,
light flux controlling member 290 allows light having been emitted
from the side surface of light emitting element 180 to enter side
surface 298 of incidence surface 292, and then emits the light
sideward through emission surface 293 toward the outside of light
flux controlling member 290.
[0058] Rear surface 191 is a planar surface disposed on the back
side of light flux controlling member 290. In the present
embodiment, rear surface 191 is disposed in the direction
orthogonal to central axis CA. The central portion of rear surface
191 has opening recess 294.
[0059] Incidence surface 292 is an inner surface of recess 294
opening toward the central portion of rear surface 191, and allows
light emitted from light emitting element 180 to enter light flux
controlling member 290. Incidence surface 292 is a rotationally
symmetrical (point-symmetrical) plane around central axis CA.
Incidence surface 292 has top surface 297 and side surface 298.
[0060] Top surface 297 is disposed to intersect central axis CA,
and corresponds to the ceiling portion of recess 294. The shape of
top surface 297 is not particularly limited. The shape of top
surface 297 may be a planar surface. In addition, top surface 297
may have a substantially conical portion at the center of the
planar surface portion. In the present embodiment, top surface 297
has a substantially conical portion at the center thereof. The
shape of top surface 297 in a plan view is circular in the present
embodiment, although the shape thereof is not particularly
limited,
[0061] Side surface 298 connects the outer peripheral portion of
top surface 297 to the opening edge of recess 294. The sectional
shape of side surface 298 in the direction orthogonal to central
axis CA is not particularly limited. In the present embodiment, the
shape of side surface 298 in the direction orthogonal to central
axis CA is circular.
[0062] Reflection surface 296 reflects light having entered
incidence surface 292 is reflected sideward. Reflection surface 296
is a rotationally symmetrical (point-symmetrical) plane around
central axis CA of light flux controlling member 290. In addition,
the generatrix line from the central portion to the outer
peripheral portion of the rotationally symmetrical plane is a curve
being concave relative to light emitting element 180, and
reflection surface 296 is a curved surface formed by rotating the
generatrix line by 360.degree. around central axis CA as a rotation
axis (see FIG. 8A). That is, reflection surface 296 has an
aspherical curved surface of which height from light emitting
element 180 is increased toward the outer peripheral portion away
from the central portion. In addition, the outer peripheral portion
of reflection surface 296 is formed at a position distant (in
height) from light emitting element 180 in the direction of optical
axis LA of light emitting element 180 compared with the center of
reflection surface 296. For example, reflection surface 296 is an
aspherical curved surface of which height from light emitting
element 180 is increased toward the outer peripheral portion away
from the central portion, or is an aspherical curved surface of
which height from light emitting element 180 (substrate 170) is
increased toward the outer peripheral portion away from the central
portion between the central portion and a predetermined point, and
of which height from light emitting element 180 is decreased toward
the outer peripheral portion away from the central portion between
the predetermined point and the outer peripheral portion. In the
former case, the inclining angle of reflection surface 296 relative
to the plane direction of substrate 170 becomes smaller toward the
outer peripheral portion away from the central portion. On the
other hand, in the latter case, reflection surface 296 has a point
at which the inclining angle relative to the plane direction of
substrate 170 is zero (parallel to substrate 170) near the outer
peripheral portion between the central portion and the outer
peripheral portion. It is noted that the term "generatrix line"
generally means a straight line to draw a ruled surface, but in the
present specification, is used as a term including a curve to draw
reflection surface 296 that is a rotationally symmetrical
plane.
[0063] Emission surface 293 emits light having entered top surface
297 and having been reflected at reflection surface 296 and light
having entered side surface 298 toward the outside of light flux
controlling member 190. Emission surface 293 is disposed to
surround central axis CA. In the present embodiment, emission
surface 293 is a curved surface along central axis CA. In the
cross-section including central axis CA, the upper end of emission
surface 293 is connected to reflection surface 296. On the other
hand, in the cross-section including central axis CA, the lower end
of emission surface 293 is connected to rear surface 191.
[0064] Also in the present embodiment, when the outer edge portion
of specular reflection area 175 is positioned closer to central
axis CA than the opening edge portion of recess 294 is to central
axis CA, light emitted from light emitting device 180 undesirably
reaches resist layer 173 directly. Thus, the light having reached
resist layer 173 results in being scattered to undesirably become
uncontrollable light.
[0065] On the other hand, when the outer edge portion of specular
reflection area 175 is positioned outside the opening edge portion
of recess 294, all the light having been emitted from the side
surface of light emitting element 180 is specularly reflected at
specular reflection area 175 to enter light flux controlling member
290 through incidence surface 292. Therefore, even when light
emitting element 180 that emits light from the side surface is
used, it is possible to properly control the distribution of light
emitted from light emitting element 180.
[0066] (Effect)
[0067] As described above, surface light source device 200 of
Embodiment 2 has the similar effects to those of surface light
source device 100 of Embodiment 1.
[0068] It is noted that, in each of the above-described
embodiments, the surface of plated layer 174 is subjected to mirror
finishing to form specular reflection area 175, but the method of
forming specular reflection area 175 is not limited thereto. For
example, specular reflection area 175 may be formed by disposing
another member having a specular reflection function on substrate
170.
INDUSTRIAL APPLICABILITY
[0069] The light emitting device and the surface light source
device according to the present invention are applicable, for
example, to a back light of a liquid crystal display apparatus, or
a generally-used illumination apparatus.
REFERENCE SIGNS LIST
[0070] 10 Back light device [0071] 20 Mounting substrate [0072] 21
Insulating layer [0073] 22 Wiring layer [0074] 23 Resist layer
[0075] 30 Package [0076] 31 Solder layer [0077] 32 Light emitting
chip [0078] 40 Diffusion lens [0079] 41 Lens part [0080] 42 Fixing
part [0081] 43 Bottom surface [0082] 44 Light incidence surface
[0083] 45 Light emission surface [0084] 46 Adhesive [0085] 50
Diffusion plate [0086] 100 Surface light source device [0087] 120
Casing [0088] 140 Light Diffusing member [0089] 160, 260 Light
emitting device [0090] 170 Substrate [0091] 171 Substrate main body
[0092] 172 Copper foil layer [0093] 173 Resist layer [0094] 174
Plated layer [0095] 175 Specular reflection area [0096] 176 Solder
layer [0097] 180 Light emitting element [0098] 190, 290 Light flux
controlling member [0099] 191 Rear surface [0100] 192, 292
Incidence surface [0101] 193, 293 Emission surface [0102] 193a
First emission surface [0103] 193b Second emission surface [0104]
193c Third emission surface [0105] 194, 294 Recess [0106] 195
Flange [0107] 198, 298 Side surface [0108] 296 Reflection surface
[0109] 297 Top surface [0110] CA Central axis [0111] LA Optical
axis
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